1. Field of the Invention
The invention relates to a catalyst for the catalytic ammoxidation of alkanes and olefins, more specifically C3 to C5 paraffins or olefins, such as propane or isobutane and propylene or isobutylene, to the corresponding xcex1,xcex2-unsaturated mononitriles, e.g., acrylonitrile and methacrylonitrile, utilizing the disclosed catalyst. In addition, the catalyst may be used in the ammoxidation of xylenes and methylpyridines to the corresponding mono- and di-nitriles.
The invention is directed also to making the catalyst containing isolated vanadium and antimony species in a matrix formed by the oxides of elements usually used as supports or diluents. The invention is directed also to using the catalyst in a process for catalytic ammoxidation of alkanes and olefins.
2. Description of the Prior Art
Acrylonitrile is industrially prepared from the ammoxidation of propylene over a metal oxide catalyst. Due to the lower cost of propane compared with propylene, much research attention has been directed towards finding a catalyst selective for the formation of acrylonitrile from propane. The majority of such catalysts are based on V-Sb oxides.
U.S. Pat. No. 3,860,534 discloses the use for ammoxidation of propane of catalysts containing only vanadium and antimony in oxidic form. British Patent No. 1,336,136 teaches that catalysts can contain, beside vanadium and antimony, only one other metal, which is disclosed to be tin. U.S. Pat. No. 4,746,641 discloses paraffin ammoxidation catalysts that contain tungsten in addition to vanadium and antimony and, optionally, tin, boron, molybdenum, gallium, iron, cobalt, nickel, chromium, manganese, zinc, selenium, tellurium, arsenic, calcium, strontium, bariun or thallium. U.S. Pat. Nos. 4,784,979 and 4,879,264 disclose processes for making a vanadium-antimony catalyst. U.S. Pat. No. 4,797,381 discloses a V-Sb based catalyst with at least one of tungsten, tin, molybdenum, boron, phosphorus, germanium, copper, silver, niobium, tantallum, titanium, iron, cobalt, nickel, chromium, lead, manganese, zinc, selenium, tellurium, gallium, indium, arsenic, an alkali metal, an alkaline earth metal or a rare earth. U.S. Pat. No. 4,871,706 discloses a vanadium-antimony catalyst with tungsten and phosphorus. U.S. Pat. No. 4,873,215 discloses tungsten and phosphorus in addition to vanadium and antimony without molybdenum in a catalyst supported on silica-alumina or alumina. U.S. Pat. No. 4,888,438 discloses a vanadium-antimony catalyst having tungsten, tin, molybdenum, boron, phosphorus or germanium and, optionally, iron, cobalt, nickel, chromium, lead, manganese, zinc, selenium, tellurium, gallium, indium, arsenic, an alkali metal, thallium, magnesium, calcium, strontium, or barium. U.S. Pat. No. 5,008,427 discloses a process of using a catalyst with titanium, tin, iron, chromium or gallium in addition to vanadium and antimony. U.S. Pat. No. 5,079,207 discloses a catalyst with tellurium or bismuth in addition to vanadium-antimony. U.S. Pat. No. 5,094,989 discloses a catalyst having an atomic ratio of antimony:vanadium is a specific range. U.S. Pat. Nos. 5,214,016 and 5,854,172 disclose a vanadium-antimony-tin catalyst. U.S. Pat. No. 5,332,855 discloses a vanadium-antimony catalyst optionally containing iron, gallium, indium or mixtures thereof. U.S. Pat. No. 5,336,804 discloses a vanadium-antimony-bismuth catalyst optionally containing iron, gallium, indium or mixtures thereof. U.S. Pat. No. 5,498,588 discloses a catalyst with vanadium and antimony with titanium, tin, iron, chromium, gallium, lithium, magnesium, calcium, strontium, barium, cobalt, nickel, zinc, germanium, niobium, zirconium, molybdenum, tungsten, copper, tellurium, tantalum, selenium, bismuth, cerium, indium, arsenic, boron or manganese impregnated with lithium, silver, iron, cobalt, copper, chromium, manganese, (VO)2+ (PW12O40)3xe2x88x92 or (PMo12O40)3xe2x88x92. U.S. Pat. Nos. 5,576,469 and 5,693,587 disclose a vanadium-antimony catalyst optionally having tin, titanium, lithium, magnesium, sodium, calcium, strontium, barium, cobalt, iron, chromium, gallium, nickel, zinc, germanium, niobium, zirconium, molybdenum, tungsten, copper, tellurium, tantalum, selenium, bismuth, cerium, indium, arsenic, boron, aluminum, phosphorus or manganese. U.S. Pat. No. 5,994,259 discloses a vanadium-antimony based catalyst in which tin, titanium or iron are optionally present. U.S. Pat. No. 6,072,070 discloses a vanadium-antimony-titanium catalyst containing TiO2 species. U.S. Pat. No. 6,083,869 discloses a co-precipitated vanadium-antimony-iron catalyst. U.S. Pat. No. 6,156,920 discloses a vanadium-antimony based catalyst which titanium, tin, iron, chromium or gallium must be present and lithium, magnesium, calcium, strontium, barium, cobalt, nickel, zinc, germanium, niobium, zirconium, tungsten, copper, tellurium, tantalum, selenium, bismuth, cerium, indium, arsenic, boron, manganese or molybdenum are optionally present. U.S. Pat. No. 6,162,760 discloses a vanadium-antimony based catalyst in which molybdenum, tungsten, niobium, arsenic, tellurium or selenium must be present and lithium, magnesium, calcium, strontium, barium, cobalt, nickel, zinc, germanium, zirconium, copper, tantalum, bismuth, cerium, indium, boron or manganese are optionally present.
Vanadium-antimony-based oxide catalysts claimed for the use in the process of ammoxidation of alkanes can comprise a single or a number of mixed vanadium, antimony and other oxides, constituting the active phase of the catalyst, or can additionally comprise another inorganic oxide, such as alumina, silica, zirconia, magnesia, titania or niobia, on which the active phase is deposited, e.g., U.S. Pat. No. 4,797,381, or with which the to active phase is mixed, e.g., U.S. Pat. No. 4,871,706, by using various techniques known in the art, such as impregnation or slurry deposition. Oxides used as supports or diluents in the catalyst art are mostly employed to improve catalyst abrasion resistance and/or to reduce its cost and do not substantially affect catalytic behavior of the active phase. The general formula of catalysts in patents do not usually include support material.
None of the above patent documents describe the use of support material as a matrix for isolation of V and Sb species in the catalyst. PCT International Application published under the number WO 00/12208 discloses vanadium antimony oxides (5 mole % of each) dispersed in and distributed by sol-gel method throughout a matrix comprising oxides of silicon, titanium, tantalum and niobium, for using as catalysts for the oxidation of butadiene to furan. There is no mention of the usefulness of these catalysts for ammoxidation reactions. Also, the patent does not disclose or suggest the vanadium antimony oxides implanted into alumina, magnesia, zirconia and hafnia to be useful catalysts. Some indication that alumina can be used as a matrix material comes from the data on propane ammoxidation over vanadium-antimony, vanadium-antimony-aluminum and vanadium-antimony-tungsten-aluminum oxide catalysts recently published by J. Nilsson et. al in J. Catalysis, 1999, 186, 442. The present invention discloses that the incorporation of oxides vanadium and antimony into an inert oxide matrix, such as alumina, zirconia, magnesia and others, improves catalytic behavior in propane ammoxidation in terms of both stability and selectivity of catalyst activity.
The present invention provides mixed metal oxide catalysts containing vanadium and antimony for the ammoxidation of paraffins to unsaturated mononitriles, in particular the amoxidation of propane and isobutane to acrylonitrile and methacrylonitrile, respectively.
The present invention provides a method for preparing mixed metal oxide catalysts containing isolated vanadium and antimony species in an inert matrix.
The present invention provides an ammoxidation process for making unsaturated mononitriles from lower paraffins, in particular for the producing acrylonitrile and methacrylonitrile from propane and isobutane, using mixed metal oxide catalysts containing vanadium and antimony in an inert matrix.
Embodiments, aspects, features and advantages of the present invention will become apparent from the study of the accompanying disclosure and appended claims.
According to one aspect of the invention, there is provided a catalyst composition comprising the elements in proportions indicated by the following empirical formula:
VSbaMbOx
where M is at least one element selected from magnesium, aluminum, zirconium, silicon, hafnium, titanium and niobium;
0.5xe2x89xa6axe2x89xa620
2xe2x89xa6bxe2x89xa650 and
x is determined by the valence requirements of the elements present.
In related aspects of the present invention, there are provided catalyst compositions comprising elements in proportions indicated by the following empirical formulae:
VSbaMbMxe2x80x2bOx
VSbaMbQcOx
VSbaMbQcQxe2x80x2cOx
where Mxe2x80x2 is selected from magnesium, aluminum, zirconium, silicon, hafnium, titanium and niobium, M and Mxe2x80x2 are different and 0xe2x89xa6bxe2x80x2xe2x89xa650; Q and Qxe2x80x2 are each one or more elements selected from rhenium, tungsten, molybdenum, tantalum, manganese, phosphorus, cerium, tin, boron, scandium, bismuth, gallium, indium, iron, chromium, lanthanum, yttrium, zinc, cobalt, nickel, cadmium, copper, strontium, barium, calcium, silver, potassium, sodium and cesium, Q and Qxe2x80x2 are different, 0xe2x89xa6cxe2x89xa610 and 0xe2x89xa6cxe2x80x2xe2x89xa610; M, a, b and x are as defined above.
In another aspect of the present invention, there are methods of preparing catalysts having the following empirical formulae:
VSbaMbOx
VSbaMbMxe2x80x2bxe2x80x2Ox
VSbaMbQcOx
VSbaMbQcQxe2x80x2cxe2x80x2Ox
where M, Mxe2x80x2, Q, Qxe2x80x2, a, b, bxe2x80x2, c, cxe2x80x2 and x are as defined above. The methods comprise precipitating mixed hydroxides from a solution or suspension of vanadium, antimony, M, Mxe2x80x2, Q and Qxe2x80x2 compounds as desired to obtain a particular catalyst composition, removing solvent from the precipitate to form a dried catalyst precursor, and calcining the resultant dried precursor at a final temperature in the range of 600 to 950xc2x0 C. to form the catalyst containing isolated V and Sb species in the MtOx or MtMxe2x80x2t.Ox matrix. In an alternative to the Q and Qxe2x80x2 elements being added and precipitated with the other elements, one or both may be impregnated on the VSbaMc solid before or after calcination.
The present invention also provides a process for making xcex1,xcex2-unsaturated mononitriles by gas phase reaction of propane or isobutane, oxygen and ammonia in the presence of a catalyst having the elements and proportions indicated by the empirical formulae:
VSbaMbOx
VSbaMbMxe2x80x2bxe2x80x2Ox
VSbaMbQcOx
VSbaMbQcQxe2x80x2cxe2x80x2Ox
where M, Mxe2x80x2, Q, Qxe2x80x2, a, b, bxe2x80x2, c, cxe2x80x2 and x are as defined above.
The catalyst may also be used in the ammoxidation of propylene and isobutylene to acrylonitrile and methacrylonitrile, and in the ammoxidation of xylenes and methylpyridines to the corresponding mono- and/or di-nitriles.